The present invention relates to network interfacing, and more particularly, to methods and systems for sending and receiving data between network stations connected to a telephone line.
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface cards at each station to share access to the media.
Conventional local area network architectures use media access controllers operating according to half-duplex or full duplex Ethernet (ANSI/IEEE standard 802.3) protocol using a prescribed network medium, such as 10 BASE-T. Newer operating systems require that a network station to be able to detect the presence of the network. In an Ethernet 10 BASE-T environment, the network is detected by the transmission of a link pulse by the physical layer (PHY) transceiver. The periodic link pulse on the 10 BASE-T media is detected by a PHY receiver, which determines the presence of another network station transmitting on the network medium based on detection of the periodic link pulses. Hence, a PHY transceiver at Station A is able to detect the presence of Station B, without the transmission or reception of data packets, by the reception of link pulses on the 10 BASE-T medium from the PHY transmitter at Station B.
Efforts are underway to develop an architecture that enables computers to be linked together using conventional twisted pair telephone lines instead of established local area network media such as 10 BASE-T. Such an arrangement, referred to herein as a home network environment, provides the advantage that existing telephone wiring in a home may be used to implement a home network environment. However, telephone lines are inherently noisy due to spurious noise caused by electrical devices in the home, for example dimmer switches, transformers of home appliances, etc. In addition, the twisted pair telephone lines suffer from turn-on transients due to on-hook and off-hook and noise pulses from the standard POTS telephones, and electrical systems such as heating and air conditioning systems, etc.
An additional problem in telephone wiring networks is that the signal condition (i.e., shape) of a transmitted waveform depends largely on the wiring topology. Numerous branch connections in the twisted pair telephone line medium, as well as the different associated lengths of the branch connections, may cause multiple signal reflections on a transmitted network signal. Telephone wiring topology may cause the network signal from one network station to have a peak-to-peak voltage on the order of 10 to 20 millivolts, whereas network signals from anther network station may have a value on the order of one to two volts. Hence, the amplitude and shape of a received pulse may be so distorted that recovery of a transmit clock or transmit data from the received pulse becomes substantially difficult.
There is a need for a network station having a physical layer transceiver capable of reliably recovering data from a received network signal on a telephone line medium.
There is also a need for a physical layer transceiver having a wide dynamic range and capable of adapting to different network signals from different network nodes on a telephone line medium.
There is also need for an arrangement in a physical transceiver receiving network signals from a telephone line medium to recover received data even if the received pulse is highly distorted.
These and other needs are obtained by the present invention, where a physical layer transceiver has an architecture enabling adaptation of detection circuitry based on the received network signal to enable reliable recovery of data signals.
According to one aspect of the present invention, a physical layer transceiver is configured for sending and receiving network signals on a telephone line medium. The physical layer transceiver includes an input amplifier for amplifying network signals received from the telephone line medium and outputting amplified received signals. A signal conditioning circuit is configured for outputting at least one of an envelope signal of the amplified received signals, and an energy signal of the amplified received signals. Slicer circuits are configured for outputting noise, peak, and data event signals indicating whether the envelope signal exceeds a noise threshold, a peak threshold, and a data transition threshold, respectively. The slicer circuits are configured for outputting energy event signals indicating with respect to time whether the energy signal exceeds an energy threshold. A digital controller is configured for controlling the noise, peak, energy, and data transition thresholds based on the noise event signal and the peak event signal. The digital controller also outputs data signals to a media access controller via a media independent interface based upon at least one of the energy event signals and the data signals. Generation of the envelope signal and the energy signal enables the digital controller to use alternative detection techniques for recovering data from the network signals, depending on the signal quality of network signals received from the telephone line medium. Moreover, the control of the noise, peak, energy, and data transition thresholds by the digital controller also enables the slicer circuits to be optimized for detecting the data events and the energy events by adjusting the different thresholds based on the noise event signal and the peak event signal.
Hence, the physical layer transceiver provides a robust data detection system, capable of adapting receiver components to optimize recovery of data signals from different types of distorted signals.
Another aspect of the present invention provides a method of receiving network signals between network stations on a telephone line medium. The method includes selectively amplifying a received network signal, received via the telephone line medium and carrying receive data from a remote network station coupled to the telephone line medium, generating an envelope signal and an energy signal of the amplified received network signal, generating a noise event signal and a peak event signal in response to the envelope signal exceeding a noise threshold and a peak threshold, respectively, successively adjusting the noise threshold and the peak threshold based on successive noise event signals and peak event signals generated within a prescribed access identifier detection interval, setting a data transition threshold based on the adjusted peak threshold, and selectively recovering the receive data based on one of;the envelope signal exceeding the data transition threshold and the energy signal exceeding an energy threshold.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.